Regarding calories expended and gained during foraging  for Sagittaria
latifolia.

I have calculated that the return on harvesting Sagittaria latifolia is 1
calorie expended for 18 gained.

The tubers float when one wades around in the soft mud and agitates its.
This ability to float assists waterfowl when they graze, and also assisted
human populations when they gathered this plant in North America. In October
while treading in the silty mud in a S.latifolia patch in water just above
my knees, 113 tubers were released from the substrate and floated to the
surface within a thirty minute time period. Keely has calculated that there
are 3.6 calories per dry gram of wapato (Keely 1980). During this trial, I
collected 1,505 grams (fresh) of wapato. Since the dry weight of wapato is
about half the weight of fresh tubers, there was caloric net of 2,709
calories of energy.  My expenditure of calories I calculate was the same as
riding a bike at a moderate pace at about 300 calories an hour. Of course if
the harvester has to break through ice to harvest it, or harvest in deep
cold water the cost effectiveness goes down.

Eating the tubers raw is ok, and there is ethnohistoic data that they were
eaten raw though usually cooked; but they not as tasty.  I don't know if all
the carbs are available uncooked.

I agree with you that we should be looking at plants such as these.  Some
plant foods require little processing; stone tools are not associated with
their use.  I think we should be also looking at that old paradigm that
stone tools as indicators of the intensification of plant use, and amend it.

Thanks

Melissa Darby

Keely, Patrick Byron

1980 Nutrient Composition of Selected Important Plant Foods of the
Pre-Contact Diet of the Northwest Native American Peoples. M.S. Thesis,
University of Washington, Nutritional Sciences and Textiles Dept.

Kubiak-Martens, L.

1996 Evidence for possible use of plant foods in Palaeolithic and Mesolithic
diet from the site of Calowanie in the central part of the Polish Plain.
Vegetation History and Archaeobotany (1996) 5:33-38.



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